The broad objective of this study is to understand the mechanisms used by the various types of kidney cells to accomplish certain functions and to determine what are the alterations at the cellular level accompanying certain disease states which affect these renal functions. Animals used in this study are selected on the basis of some specialized structure or function which makes them advantageous in an attempt to delineate a relationship between renal morphology and renal function. This study proposes to alter certain physiological conditions in animals, or to administer specific drugs to animals, and to correlate the physiological and pathological state thus produced with renal morphology utilizing descriptive techniques, histochemistry, freeze-etch, and radioautography on both light and electron microscopical levels. Studies of cellular mechanisms under normal and abnormal conditions should prove useful in obtaining a deeper understanding of renal diseases and perhaps lead to a rational approach to therapy.